Puerto Rico Student Test Bed

ByVíctor Marrero-Fontánez

Manuel A. Vega-CartagenaCASA SLC Members

UPRM Graduate Students

Overview

• What is CASA?– Student Test Bed (STB)

• Magnetron Radar– Quantitative Precipitation Estimation (QPE) Study– Data Validation– Radar Specifications

• Off-the-Grid Radar– Antenna

What is CASA?

• Collaborative Adaptive Sensing of the Atmosphere• NSF Engineering Research Center Program

– Established in 2003• Objective

– To create a new engineering paradigm in observing, detecting and predicting weather and other atmospheric phenomena.

• Partner Universities– University of Massachusetts– Colorado State University– University of Oklahoma– University of Puerto Rico at Mayaguez

Student Test Bed

• Objective– To establish a QPE sensing network starting in

the western end of the island taking into consideration coverage gaps from NEXRAD.

• Radar Sites– Three sites were selected based on geographical

data and sociological impact. These are located in Mayagüez, Aguadilla and Lajas.

Student Test Bed

QPE Study

• Quantitative Precipitation Estimation– One of main efforts of CASA– Studies using 2-D video disdrometer performed– QPE using attenuating wavelength

• X-Band Radar

QPE Study

• Path-Integrated Attenuation (PIA)– Study performed by Delrieu et al. [1]

• Grenoble, France– Surface Reference Technique– Ratio of mountain returns

• Presence and absence of rain– Later used for rain rate calculations

• Rain rate retrieval algorithm not yet selected

QPE Study

• Methodology– Low elevation angle– Identify mountain cluttered radar bins using

apparent reflectivity• Calculate average Za over cluttered bins during dry

period• Compare to average Za during rain event

– Perform rain rate retrieval

Data Validation

• Several Tipping-Bucket Rain Gauges– Located along propagation path

• Joss Waldvogel Impact Disdrometer – Rain Drop Size Distribution (DSD)– Expected Reflectivity Calculations

Radar Specifications

• Raytheon Marine X-Band Radar• Single Polarization

– Magnetron• F = 9.41 GHz• Ppeak = 25 kW

• Duty Cyclemax = 0.001

Radar Specifications

• Modifications– Antenna

• 1.22m Parabolic Dish

• G = 38 dB• 2.0˚ HPBeamwidth

– Spinner• Originally 25 RPM• Lowered to 3 RPM

Radar Specifications• Modifications

– Data System• Linux based Mini-ITX embedded

system• 12 Bit ADC for sampling video

signal• 802.11b data transport to data

archive server– Control

• FPGA on PCI bus for timing signals and antenna position encoder data

Radar Specifications

• Location– Roof of electrical

engineering building at UPRM

– Tower already installed

Radar Specifications

Attenuator

M

Raytheon X-Band RadarModified Front End

Diagram

VCO

Magnetron

Power Sampler

9.41 GHz

Antenna

Circulator

Noise Source

Power Combiner

Limiter

PIN Switch (Reflective)

LNA

IR Mixer

IF60MHz

9.470 GHz

IL = 0.5 dB

Pmax = 26 dBm

IL = 0.85dB

Isolation = 25 dB

Isolation ≥ 67 dB

Gain = 7.0 dB

F = 3.5 dB

Receiver Noise Figure = 8.00 dB

ENR = 15.5 dB

Receiver Dynamic Range = 91.74 dB

ToData

System

50 dB

35 dB

P = 25 kW = 74 dBm

RaytheonHV

Modulator Board

Load IL = 2 dB

IL = 0.4 dB

Isolator

HPBeamwidth = 2.0°Gain = 38.0 dBi

P1dB = -8 dBmCalibration Loop

OTG AntennaSingle polarization 16 x 16 antenna array• Physical size: 17” by 17”

• Material: TLY-3 from Taconic

• Er = 2.2, h = 0.787mm

• Resonant Frequency = 9.38GHz[*]

• Antenna tested in RadLab.

• The antenna did not perform as expected.

[*] result given by Designer

OTG Antenna• BW of single-pol

antenna: 9.25 - 9.6 GHz [VSWR < 2].

• Higher side-lobes in left side of the pattern due to undesired radiation in the corporate feed.

[measured in Radiation Lab.]

OTG Antenna

Dual polarization patch antenna

• A multi-layer antenna is under design for dual polarization.

• Both polarizations are fed by aperture coupling.

• The array antenna will have rows of these patches connected in series.

• Resonant Frequency: 9.5 GHz [*]

• Cross-polarization: Around 29 dB for a single patch for each polarization is expected.

• This patch exhibits linear polarization and/or circular polarization if desired.

Latest Achievements

• Radar antenna moved to Stefani building rooftop.

Questions

References[1] Delrieu, G. et al., “Rain Measurement in Hilly Terrain with X-Band Weather Radar

Systems: Accuracy of Path-Integrated Attenuation Estimates Derived from Mountain Returns ”, Journal of Atmospheric and Oceanic Technology, Vol. 16, pp. 405-415, April 1999.

[2] Rincón, R.F. et al. “Estimation of Path-Average Rain Drop Size Distribution using the NASA/TRMM Microwave Link”, IEEE International Geoscience and Remote Sensing Symposium (IGARSS), Vol. 3, 9-13 July, 2001.